Users Guide

3 Packet 2 is also forwarded to the ingress interface with an unchanged destination address because it
does not have broadcast address configured.
Figure 47. UDP Helper with Broadcast-All Addresses
UDP Helper with Subnet Broadcast
Addresses
When the destination IP address of an incoming packet matches the subnet broadcast address of any
interface, the system changes the address to the configured broadcast address and sends it to matching
interface.
In the following illustration, Packet 1 has the destination IP address 1.1.1.255, which matches the subnet
broadcast address of VLAN 101. If you configured UDP helper and the packet matches the specified UDP port,
the system changes the address to the configured IP broadcast address and floods the packet on VLAN 101.
Packet 2 is sent from the host on VLAN 101. It has a broadcast MAC address and a destination IP address of
1.1.1.255. In this case, it is flooded on VLAN 101 in its original condition as the forwarding process is Layer 2.
Figure 48. UDP Helper with Subnet Broadcast Addresses
IPv4 Routing 472